Intumescent composition

ABSTRACT

An intumescent composition which comprises a polymer selected from a silane-terminated polyurethane or a silane-terminated polyether, a plasticizer that is compatible with the polymer and an intumescent ingredient. Processes of forming a cured intumescent substance, and methods of fire protecting a building are also provided.

FIELD OF THE INVENTION

The present invention relates to an intumescent composition and its usein fire protection.

BACKGROUND OF THE INVENTION

Buildings having steel frameworks are particularly vulnerable tocollapse in the event of a fire. Steel loses its strength as thetemperature rises. By insulating the steel, the rate of heat transfercan be reduced, which can extend the time the building remains intact,giving more time for evacuation.

Passive fire protection is the term generally given to systems whichrely on insulation to protect buildings from fire. Passive fireprotection may be “reactive” or “non-reactive”. Reactive systems arebased on insulation which changes its physical and/or chemical nature inresponse to fire. Examples include intumescent, oblative and sublimingsystems. Non-reactive systems provide insulation without the need forany chemical or physical change. Examples include cementitious spray andvermiculite board.

Fire-protective coatings may be applied to steel framework for buildingseither off-site (in the steel yard) or on-site (to the erectedframework). Typical intumescent systems are based on a mixture ofammonium polyphosphate and melamine. These react to produce N₂ gas whichresults in a layer of foam several centimetres thick which insulates theframework.

Conventional one-component intumescent compositions are either solventor water-based and form a dry film through evaporation of the solvent orwater. This characteristic places practical limits on the maximum wetfilm thickness that can be applied in any one coat, as thick films tendto take a long time to dry.

Two-part epoxy resin based coatings have been used by Leigh's Paints toprovide fire protective coatings on steel. Such coatings have excellentadhesion to steel, are hardwearing and rely on intumescence to providefire protection.

Similarly, CharTek have developed a variety of products for use as fireprotective coatings. CharTek 7, for instance, is a solvent-free,reinforced epoxy intumescent fire proofing coating, suitable to protectsteelwork in a hydrocarbon fire.

Fire protective intumescent coatings are described extensively in thepatent literature. US 2008/0224105 A1, for instance, describes a liquidintumescent coating composition comprising a resin system. The coatingcomposition is curable to a solid state in a free radical polymerisationreaction. WO 2008/129242 describes an intumescent formulation comprisinga source of carbon, a blowing agent, an acid source and clay such as anorganoclay. The organoclay is thought to improve the thermal barrierproperties of a foamed intumescent coating. WO2009/013532 describes acoating composition which comprises at least one intumescent ingredientincorporated into a resin binder which contains at least one covalentlybonded phosphorous containing component.

However, these prior art compositions have limitedintumescence-generating ability and as a result, thick layers of thecompositions are required, which can be very expensive.

SUMMARY OF THE INVENTION

The present invention provides in a first embodiment an intumescentcomposition comprising a polymer selected from a silane-terminatedpolyurethane or a silane-terminated polyether, a plasticiser that iscompatible with the polymer and an intumescent ingredient.

According to a second embodiment of the invention there is provided aprocess for forming a cured intumescent substance comprising applying acomposition according to the first embodiment to a substrate andallowing the composition to cure.

According to a third embodiment of the present invention, there isprovided a cured intumescent substance obtainable by the process asdescribed in the second embodiment.

According to a fourth embodiment of the present invention, anintumescent composition according to the first embodiment is used in afire-protective coating.

According to a fifth embodiment of the present invention, there isprovided a building comprising a steel framework comprising the curedintumescent substance of the third embodiment.

By “intumescent composition” is meant a composition that is able toexpand, or swell, when exposed to heat.

The intumescent compositions of the invention can be used to coatsubstrates such as steel intended to form building frameworks eitheroff-site (during the steel preparation process) or on-site (after thesteel framework has been laid in place at the site of the building). Athigh temperatures, the silane-terminated polyurethane or polyetherbreaks down. This is advantageous, since in the event of a fire, thepolymer does not interfere with the intumescence generated by theintumescent ingredient.

The composition of this invention has high intumescence efficiency whichmeans that relatively thin coatings can be applied to steel frameworks,which results in faster cure time and a more efficient and cheaperfire-protective process.

Ideally, each 1.5 mm of coating thickness will cure in one hour or less.This offers particular advantages over the prior art one-componentsystems which may require five or more coats to be applied, with up totwo weeks for drying between coats.

The compositions of the invention have additionally been shown to haveearly weathering resistance compared to the prior art. The compositionsare resistant to mechanical damage and are non-toxic and easy to repairwhen damaged, compared with epoxy or the one-component systems detailedabove.

The prior art also discloses many compositions comprising fire retardantmaterials. Fire retardant materials suppress, reduce or delay thecombustion of material. The present invention, on the other hand relatesto intumescent compositions. These compositions provide fire protectionvia expanding, or swelling, when exposed to heat, thus increasing involume.

DETAILED DESCRIPTION OF THE INVENTION

According to one aspect of the present invention, there is provided atwo-part intumescent composition comprising a first part and a secondpart. The first part comprises a polymer selected from a silaneterminated polyurethane or a silane terminated polyether, wherein thispolymer is present in an amount of up to 100% by weight of the firstpart of the intumescent composition. The second part comprises aplasticiser that is compatible with the polymer and an intumescentingredient typically present in an amount of 1-80% by weight of thesecond part of the composition. The amount of polymer present in thefirst part generally makes up 4-50% by weight of the first and secondparts taken together. The first and second parts are separated from oneanother, for instance during storage, but in use, the first and secondparts are mixed to achieve a cured substance which has the ability tointumesce on exposure to heat.

Preferably, in the two-part composition, there is a greater proportionby weight of the second part compared to the first part. In aparticularly preferred embodiment of the invention, the ratio offirst:second part is in the range 1:5 to 1:20 by weight.

In one-part compositions, all of the considerations mentioned below withregard to two-part compositions apply mutatis mutandis, save that theconstituents are all mixed together and not separated into two parts,and that any ‘wet’ ingredients need to be dried prior to manufacture ofthe composition in order to prevent premature cure.

The silane terminated polyurethane or a silane terminated polyether istypically a liquid. The polymer gives rise to a cured composition havinga 48-hour Shore A hardness of 65-85, preferably 70-80. The Shore Ahardness is determined in accordance with the method described in the“Methods” section of this specification.

The polymer is present in an amount of up to 100% by weight of the firstpart of a two part composition, such that the amount of polymer presentmakes up 4-50% by weight, more preferably 5-20%, and most preferably 10%by weight of the first and second parts of the intumescent compositiontaken together. Preferably the first part of the two-part compositionconsists essentially of polymer, and more preferably consists solely ofpolymer. When the first part consists solely of or consists essentiallyof polymer, the first part is in the form supplied by the manufacturer,with no further processing or mixing required prior to delivery to theend user (compounding). This reduces the processing cost and speedsmanufacture of the two-part composition. Further it avoids the need forthe polymer to be extensively handled, and hence increases shelf life byreducing contamination or the inadvertent incorporation of atmosphericmoisture.

In one-part compositions, the amount of polymer present typically makesup 4-50% by weight, more preferably 5-20%, and most preferably around10% by weight of the intumescent composition.

Preferably the polymer is a telechelic polymer (ie. a polymer carryingat least one functionalised end group that has the capacity forselective reaction to form bonds with another molecule). More preferablythe polymer is a telechelic polymer with difunctional or trifunctionalend groups. Even more preferably both ends of the polymer have at leastone functionalised end group, and most preferably both ends of thepolymer have at least two functional end groups. Preferably the polymerend groups result from the termination with an alpha or gamma silane.Most preferably, the end groups result from termination with analpha-silane. Preferably the terminal functionalities are alkoxy groups,such that difunctional end groups give rise to two alkoxy groups pendantfrom the Si atom in a silane terminating group, and such thattrifunctional end groups give rise to three alkoxy groups pendant fromthe Si atom in a silane terminating group. Preferably the polymer is ofa low viscosity, for example 5,000-35,0000 mPas at 25° C. Typically thealkoxy group content of the polymer is 0.35-0.70 mmol/g, and preferablyit is 0.35-0.70 mmol/g. More preferably the alkoxy group content is0.40-0.50 mmol/g. Most preferably the alkoxy group content is a methoxygroup content.

Examples of suitable polymers include Polymer ST61, Polymer ST75 andPolymer ST77 supplied by Hanse Chemie; Geniosil STP E10, Geniosil STPE15, Geniosil STP E30 and Geniosil STP E35 supplied by Wacker; DesmosealSXP 2662, Desmoseal SXP 2458 and Desmoseal SXP 2636 supplied by Bayer;and Spur⁺* 1010LM, Spur⁺* 1050LM and Spur⁺* 1015LM supplied byMomentive. Preferred polymers are Geniosil STP E10 and STP E30 bothsupplied by Wacker. The most preferred polymer is Geniosil STP E10.

Preferably, at least one of the parts of a two-part composition, or theone-part composition comprises a cross-linker. A cross-linkeraccelerates the curing process. Preferably the cross-linker is areactive silane crosslinker, more preferably an alkoxy silane whichcontains a reactive functional group, which is most preferably a primaryamine. This cross-linker is preferably present at 0.05-1% by weight ofthe total composition.

Most preferably the cross-linker is in the first part of a two partcomposition.

The composition may also comprise a solvent to reduce viscosity andimprove the sprayability of the composition. Typically the solvent is inthe first part of a two-part composition. The solvent is chosen on thebasis of compatibility with the polymer component. In the case ofGeniosil STP E10, a suitable solvent is xylene.

The composition of this invention comprises a plasticiser and anintumescent ingredient. Typically these are in the second part of atwo-part composition.

Looking first at the plasticiser, this must be compatible with thepolymer and by this we mean that it will mix into the system withoutbleeding back out. The plasticiser has the function of softening andextending the final cured polymer network, and providing extra liquidcomponents so that the mineral fillers are fully wetted-out. Theplasticiser can be present in any amount sufficient to fulfil thispurpose. Typical amounts of plasticiser are 5-20% of the second part,preferably 10-15% of the second part. Suitable plasticisers arederivatives of benzoic acid, phthalic acid (eg. phthalates, such asdibutyl-, dioctyl-, dicyclohexyl-, diisooctyl-, diisodecyl-, dibenzyl-or butylbenzyl phthalate), trimellitic acid, pyromellitic acid, adipicacid, sebacic acid, fumaric acid, maleic acid, itaconic acid and citricacid, alkyl phosphate esters and derivatives of polyester, polyether andepoxy and the like. Preferred plasticisers are alkyl esters for examplephthalates, adipates, sebacates and benzoates, which may be blendedtogether and blended with alkyl phosphate esters. An especiallypreferred example is a blend of Jayflex DNIP supplied by Exxon, withPlastomoll DOA, supplied by BASF, and Santicizer 148, supplied by Ferro.Castor Oil or similar natural products may also be used.

Typical amounts of plasticizer in a one-part composition are 10-40% byweight, preferably 15-30% by weight and most preferably around 20% byweight of the total composition.

The intumescent ingredient imparts on the resultant intumescentcomposition the ability to swell when exposed to heat. The ingredient istypically provided in the form of an intumescent filler compositionwhich comprises two or more ingredients, which together result inintumescence.

The intumescent filler composition (which may alternatively be referredto as an “intumescent filler package”) preferably comprises threecomponents—an acid source, a carbon source and a spumific or gas source.Preferably an inorganic “nucleating agent” should be present andoptionally additives, which may be solid or liquid by nature, may beadded to aid char (foam) formation and strengthen the char.

The acid source may be selected from, for instance, ammoniumpolyphosphate, melamine phosphate, magnesium sulphate and boric acid.The preferred acid source is ammonium polyphosphate.

The use of coated ammonium polyphosphate is preferred, and ammoniumpolyphosphate coated with melamine formaldehyde is most preferred.

The acid source preferably constitutes from 35% to 65% by weight of theintumescent ingredient content of the intumescent composition.

Examples of suitable carbon sources include polyhydric alcohols such aspentaerythritol and dipentaerythritol. Starch and expandable graphiteare other possible carbon sources. The preferred carbon sources arepentaerythritol and dipentaerythritol or a combination of the two.

The carbon source preferably constitutes from 5% to 40% by weight of theintumescent ingredient content of the intumescent composition.

Suitable gas sources include melamine, melamine phosphate, melamineborate, melamine formaldehyde, melamine cyanurate, tris-(hydroxyethyl)isocyanurate (THEIC), ammonium polyphosphate and chlorinated paraffin.The preferred gas source is melamine.

The gas source preferably constitutes from 5% to 40% by weight ofintumescent ingredient content of the intumescent composition.

Although not an essential ingredient in intumescent reactions, inorganic“nucleating” agents are a preferred ingredient since they promote sitesfor the intumescent char to form, improve the thermal resistanceproperties and stability of the intumescent char during a fire. Theintumescent coating compositions of the present invention ideallycontain at least one nucleating agent, examples of which includetitanium dioxide, zinc oxide, aluminium oxide, silica, silicates, heavymetal oxides such as cerium oxide, lanthanum oxide and zirconium oxide,mica and bentonite clay. A preferred nucleating agent is titaniumdioxide which also provides opacity to the coating.

The nucleating agent preferably constitutes from 1% to 25% by weight ofthe intumescent ingredient content of the intumescent composition.

Further optional additives may be included as part of the intumescentingredients to aid char formation and to strengthen the char and preventchar degradation. Such additives include solids such as zinc borate,zinc stannate, zinc hydroxystannate, glass flake, glass spheres,polymeric spheres, fibres (ceramic, mineral, glass/silica based),aluminium hydroxide oxide, boron phosphate, fumed silica.

In a preferred aspect of the invention, the intumescent ingredient ispresent in amount such that the composition is capable of swelling to atleast three times, preferably at least ten times, most preferably atleast 50 times its original volume when exposed to temperatures found ina typical fire situation. The temperature in a fire can be anywhere inthe range 150-1000° C. and it is preferred that the composition startsto intumesce at a temperature in the lower part of this range. Thereference temperature for measurement of swelling can be taken to be500° C.

By expansion ratio is meant the number of times the composition swellscompared to its original volume.

Typically, the intumescent composition of the invention swells to morethan 300%, preferably more than 1000%, more preferably more than 5000%of its original thickness when in the form of a coating and exposed toheat at a temperature of 500° C. For instance, the composition may beapplied to a substrate to form a layer approximately 1 mm thick aftercuring. Upon exposure to heat at a temperature of 500° C. this may swellto a thickness in the range 5-10 mm.

A typical intumescent filler package includes titanium dioxide,pentaerythritol, dipentaerythritol, ammonium polyphosphate, melamine andmelamine containing compounds such as melamine phosphate and melaminecyanurate. Preferably, the fillers are as shown below and are present inthe following amounts:

-   -   Titanium dioxide (5-15% by weight of total composition)    -   Pentaerythritol (5-15% by weight of total composition)    -   Amonium polyphosphate (20-40% by weight of total composition)    -   Melamine (5-15% by weight of total composition)

The total amount of intumescent ingredient, for instance, theintumescent filler composition, is typically in the range 40-80%,preferably 50-75% and most preferably 55-75% by weight of the totalcomposition. Compositions comprising less intumescent ingredient thanthis are not so effective at producing intumescence.

The filler may also comprise intrinsically intumescent polymers or saltsof such polymers. These proprietary materials have been developed byPrometheus Developments Limited, and are described in US PatentApplication No. US2007/0102686A1.

The composition (in the case of a two-part composition, typically thesecond part) can also contain UV absorbers/stabilisers (for exampleUvasorb HA supplied by 3V International SA or Tinuvin 765 supplied byCiba); antioxidants (for example Irganox 245 or 1135 both supplied byCiba); colour pigments or dyes (for example a carbon black, one exampleof which is Printex V supplied by Grohlman; or a titanium dioxide, oneexample of which is Kronos 2300 supplied by Kronos Ltd); rheologymodifiers, such as clays (for example the Polywhite E from Imerys orGaramite from South Clay Products); or reaction catalysts (for example atin catalyst, one example of which is Tinstab BL277 supplied by PolyoneCo. Ltd), or wetting agents (such as fatty acid derivatives, one exampleof which is Dispers 652 from Tego Chemie); or structuring fibres such asrockwool.

The composition of the invention is typically a coating composition andforms a film on surfaces to which it is applied.

According to a second embodiment of the present invention, there isprovided a process for achieving a cured intumescent substance. In thecase of a two-part composition this process comprises the steps of (a)applying a first part of a two-part intumescent composition and a secondpart of a two-part intumescent composition to a substrate, and (b)allowing the first part of the two-part intumescent composition and thesecond part of the two-part intumescent composition to cure by allowinga reaction between the first part and the second part to proceed.Typically, the first part and the second part of the two-partcomposition are mixed together prior to application to the substrate.Preferably this pre-mixing occurs very shortly before application to thesubstrate, for example a few seconds before application in an on-linemixer incorporated into an airless spraying apparatus, or by means ofany other spraying apparatus conventionally used to mix and apply twocomponent coatings to substrates.

A one part composition may be applied using a similar sprayingapparatus.

The composition used in this process has all of the same features asoutlined above for the first embodiment of this invention.

As mentioned above, the two-part composition of the invention is curedby bringing the first part and the second part of the compositiontogether, and allowing atmospheric moisture to initiate crosslinking ofthe polymer in the first part. This crosslinking can be furtherencouraged by addition of an adhesion promoter or cross-linker (such asSilane A1110 and Silane A171 both supplied by Momentive PerformanceMaterials) into the second part of the composition.

The ratio of the first to second parts is generally recommended by theparticular manufacturers and depends on the particular formulation ofthe parts.

A one-part composition cures by exposure to atmospheric moisture in thesame manner.

The composition of the invention preferably provides a steel body withfrom 30 minutes to 4 hours of fire resistance, depending on theapplication, nature and geometry of the substrate and the coatingthickness. Fire resistance is determined in accordance with BS476 Part20. Preferably the steel body takes from 30 minutes to 4 hours, and mostpreferably at least one hour, to reach a critical failure temperature of550° C.

Once the composition of the invention has fully cured, the 48 hour ShoreA hardness is typically in the range of 65-85, preferably 70-80. Themethods used to establish these values are set out below in accordancewith the method described in the “Methods” section of thisspecification.

The intumescent compositions of the present invention are used tofire-proof buildings. The composition may be applied to the framework ofthe building, typically made of steel, either in the metal-forming plant(“off-site”) or on-site after the framework has been erected. This mayrequire the surface of the metal to be cleaned in a pre-treatment step.The surface may then need to be covered with a primer layer.

Steel sections requiring fire protection are normally blast cleanedprior to the application of an intumescent coating to remove millscaleand other deposits that may lead to premature failure of the intumescentcoating, either on prolonged atmospheric exposure or during a firesituation. In order to prevent deterioration of the blast cleanedsurface, particularly where there is a delay in applying the intumescentcoating, it is normal practice to apply a primer coating. This is oftenthe case when the intumescent coating is applied on site.

Examples of suitable primers are coatings based on epoxy, modified epoxy(such as modified with polyvinyl butyral), polyurethane, acrylic, vinyland chlorinated rubber. Primers based on epoxy are preferred.

The thickness of the primer is ideally in the range from 15 microns to250 microns. Preferably the thickness should be in the range from 25microns to 100 microns.

Thereafter, the composition of the invention may be applied. Thetwo-parts of a two-part composition are typically mixed very shortlybefore application to the metal. The composition is generally sprayedonto the metal, although it may alternatively be applied manually, forinstance using an implement such as a trowel. The composition isnormally applied in separate layers, the thickness of each layer and thenumber of layers being determined by the desired speed of applicationand time of fire protection. Applying a single, relatively thick layergives a fast rate of application (but may take longer to cure). Applyingmultiple, relatively thin layers gives a smoother and more visuallyappealing decorative finish. The dry thickness of intumescent coatingapplied typically varies from 250 μm to 5 mm depending on the level offire protection required, the cross-sectional area of the steel and theperimeter of the steel when viewed in cross-section.

A decorative topcoat may be applied to the cured intumescent coatings ofthe present invention, particularly to provide colour to exposedsteelwork. A topcoat if correctly formulated will also enhance thedurability of the intumescent coating compositions. A clear sealer mayalso be suitable.

Examples of suitable decorative topcoats are coatings based on epoxy,polyurethane, alkyd, acrylic, vinyl and chlorinated rubber. Decorativetopcoats based on urethane or epoxy are preferred.

The thickness of the decorative topcoat can vary from 15 microns to 250microns. Preferably the thickness should be in the range from 25 micronsto 75 microns, as too high a thickness of topcoat may inhibit theintumescent reactions.

Compositions of the invention may also be useful in protecting otherstructural materials such as concrete and timber.

Methods Brookfield Viscosity:

This test is a simple method for the determination of the viscosity ofvery viscous materials. It uses a Brookfield RVT Viscometer and a T-barspindle.

The spindle is attached to the viscometer which rotates the bar at aknown speed (which may be varied from 0.5-100 rpm). The viscometermeasures the resistance to rotation and this is translated to ameasuring scale. The measurement is taken when the reading on the scalestabilises and a conversion calculation (according to the Brookfieldmanual) is carried out to yield a value of viscosity.

The mixed viscosity is normally measured for this material as this givesa good indication of whether the material is sprayable or not.

Due to the short pot life of the mixed material, a “dummy” part B isused, with the reactive silane replaced with an inert liquid (such asSovermol 1058, a non-reactive diluent available from Cognis GmbH) ofsimilar viscosity.

Firstly the material is conditioned to a temperature of 20±1° C.

Spindle 7 is normally used, although other spindles may be substitutedto deal with higher or lower viscosity materials, and measurements aremade at 1, 2.5, 5, 10, 20, 50 and 100 rpm. In each case, viscosity isrecorded after 60 seconds has elapsed at that speed.

Shore Hardness:

The hardness of plastics is most commonly measured by the Shore test.This method measures the resistance of plastics toward indentation andprovides an empirical hardness value that does not necessarily correlatewell to other properties or fundamental characteristics. The Shore Ascale is used for “softer” plastics and rubbers while the Shore D isused for “harder” ones.

The Shore hardness is measured with an apparatus known as a Durometerand consequently is also known as “Durometer hardness”. The hardnessvalue is determined by the penetration of the Durometer indenter footinto the sample. Because of the resilience of rubbers and plastics, theindentation reading may change over time—so the indentation time issometimes reported along with the hardness number.

In our case, we use a standard Shore A durometer which applies a forceof 822 grammes to a hardened steel foot in the shape of a truncated 35°cone, 0.79 mm in diameter. The force is applied for one second and thehardness is read off the dial.

4-hour, 24-hour and 48-hour versions of the test refer to the curingtime that the material is allowed before the hardness is measured.

A 4 mm thick wet film is spread onto a flat steel panel using a filmspreader. The film is then left in ambient conditions and the tack freetime is recorded. The Shore A hardness is measured at intervals.

Tack-Free Time:

This is the time needed for the material to cure to the extent thattouching the surface of the material no longer leads to uncured sealantbeing transferred to the fingers. In practice, it is the time at whichthe material can be handled. As such, the Tack-free Time is measured bytouching a sample with a gloved finger at intervals, until no transferto the glove is detectable to the person touching the sample.

Fire Testing

Fire testing of intumescent compositions for structural steel isnormally carried out using a furnace to simulate the effect of a fullydeveloped fire in a room or building compartment. These furnaces arenormally either natural gas, liquid petroleum gas or diesel fuelled andconsist of a number of burners mounted in the walls of a refactoryenclosure. Modern equipment is computer controlled to followpredetermined heating curves, normally to ISO834, and maintain a setpressure, normally around 20 Pa. The furnaces vary in size from afraction of a cubic meter to the typical “floor furnace” used to testintumescent compositions at independent test houses which are normallyabout 4 m long by 3 m wide by 2.5 m high.

There are many fire test standards applicable to intumescentcompositions for structural steel across the world, these include BS476part 20, EN13381 part 8 (published in draft), ISO834 part 11 (indevelopment) and UL263. These all involve the preparation of a number ofspecimens of structural steel of different sizes, geometries and weightscoated with different thicknesses of intumescent which are exposed tothe heat of the furnace for periods between 30 minutes and four hours.The temperature rise of each sample is measured using thermocouples andrecorded. This data is then used to create a comprehensive set oftables, using interpolation or mathematical modelling, that defines thethickness of intumescent required to limit the temperature rise of aparticular steel section to a particular limiting temperature for thefire protection period required.

The critical temperatures recorded in the Examples below record thefailure temperature of the steel. Different structural elementsgenerally fail at different temperatures. For instance, columns(vertical members) typically fail at 550° C., whereas beams (horizontalmembers) typically fail at 620° C. Flat plates used in laboratorytesting fail at 500° C.

One-Part Composition

For the one-part composition, a 0.6 mm nominal thickness coating wasapplied to a 5 mm thick steel panel of dimensions 300×200 mm. The panelwas primed with Nullifire S620 primer, a 1 pack alkyd primer. This panelwas left to cure for 1 week before being fire tested in the NullifireMini Furnace to the BS 476 pt20 heating regime. The Nullifire minifurnace has dimensions 0.5×0.5×0.5 m and is gas-fired to atemperature >1000° C. The time taken for the steel panel to reach aparticular critical temperature is recorded.

Two-Part Composition

The fire testing for the 2 part composition was carried out with brushapplied specimens and according to BS 476 pt 20 on the Nullifire 1.5 m³furnace, which has dimensions 1.5×1.5×1.5 m. The dimensions of the steelsample under test and the dry film thickness (DFT) of the coating areoutlined further below.

The rate of heating of steel is dependent on the H_(P)/A value of thesection, where the H_(P) is the perimeter of the steel when viewed incross-section, and A is the cross-sectional area.

The invention will now be illustrated by way of the following examples:

Control Example

The temperature rise of an unprotected piece of structural steel infurnace conditions according to ISO834 has been measured experimentallyon many occasions, for example by British Steel, and is well known andis documented in publications such as BS5950 part 8. The equation time,t=0.54×(limit temp−50)×(Hp/A)−0.6 is given in BS5950 part 8 and predictsa time to 620° C. of only around 14 minutes for unprotected steel for a406 mm×178 mm×60 kg universal beam coated with 4 mm of intumescentcoating, mounted in the roof of a 1.5 m×1.5 m a 1.5 m gas fired furnace.

Example 1 One Part Composition

Component Function % wt Trade name Supplier STP Polymer 9.98 GeniosilWacker Polymer STP-E10 DOA Plasticizer 19.91 Plastomoll BASF DOA RutileIntumescent 13.00 Kronos 2300 Kronos Titanium Filler DioxidePentaerthyritol Intumescent 11.34 Charmor Perstorp Filler PM40 MelamineIntumescent 9.68 Melamine BASF Filler Zinc Borate Intumescent 1.27Firebrake ZB 20 Mule Filer Team Ammonium Intumescent 33.74 Exolit Ap422Clariant Polyphosphate Filler Gamma- Cross-linker 1.11 Silane Momentiveaminopropyl A1110 trimethoxy silane

Properties:

Viscosity: (Brookfield, spindle 6, 20 rpm, 20° C.)=270-330 PoiseHardness development:(4 hrs tack free time)

8 hrs:30-35 Shore A 16 hrs:55-60 Shore A Fire Test:

Nullifire Mini Furnace (DFT=0.65 mm) time to 500° C.=35 minutes

Example 2 Two-Part Composition (Sprayable)

1^(st) Part Component Function % wt Trade Name Supplier STP PolymerPolymer 80 Geniosil STP- Wacker E10 Gamma- Cross- 8.9 Silane A1110 Mo-aminopropyl linker mentive trimethoxy silane Xylene Solvent 11.1

2^(nd) Part Component Function % wt Trade Name Supplier Dioctyl adipatePlasticizer 4.59 Plastomoll BASF DOA Diisononyl pthalate Plasticizer4.59 Plastomoll BASF DINP Isodecyl Plasticizer 4.59 Santicizer Ferrodiphenylphosphate 148 Xylene Solvent 9.68 Rutile Titanium Intumescent12.74 Kronos 2300 Kronos Dioxide Filler Pentaerythritol Intumescent11.21 Charmor Perstorp Filler PM40 Melamine Intumescent 11.21 MelamineBASF Filler Ammonium Intumescent 34.15 Exolit AP422 Clariantpolyphosphate Filler Fatty Acid Dispersing 0.76 Disperse Tego derivativeadditive 652, Evonik Alkyl Quaternary Thixotropic 2.04 Garamite RockwoodAmmonium clay agent 1958 Additives Ltd China Clay Thickening 2.55Polywhite E Imerys Agent Minerals Ltd Benzenepropanoic Anti-oxidant 0.76Irganox 1135 Ciba acid, 3,5-bis (1,1- dimethyl-ethyl)-4- hydroxy-, C7-C9branched alkyl esters Man-made Silicate Char 1.12 lapinus Lapinus fibresreinforcement Roxul 1000 Fibres BVMixing ratio 1^(st) part to 2^(nd) part=11.5:100

Properties:

Viscosity: mixed, spindle 7, 50 rpm, 20° C. 300-340 PoiseHardness development: Tack free time: 45-60 minutes

-   -   2 hrs 40-45 Shore A    -   3 hrs 50-55 Shore A    -   6 hrs 60-65 Shore A    -   24 hrs 75-80 Shore A

Fire Testing:

Universal Column, 203×203×52, Hp/A 180 m⁻¹, DFT 3.8 mm. Nullifire 1.5 m³Furnace, to BS 476 pt20Time to Critical Temperature (550° C.)=93 minutes

Expansion ratio measured on a steel panel in a 600° furnace=23. Onset ofintumescence was at 315° C.

Example 2 was repeated using the same 1^(st) part and 2^(nd) partcomponents. However, the first and second parts were mixed in the ratio1^(st) part to 2^(nd) part of 25:10. Very little intumescence wasdetectable.

Example 3 Two Part Composition Trowelable (No Solvent)

1^(st) Part Component Function % wt Trade Name Supplier STP PolymerPolymer 90 Geniosil STP- Wacker E10 Gamma- Cross- 10 Silane A1110 Mo-aminopropyl linker mentive trimethoxy silane

2^(nd) Part Component Function % wt Trade Name Supplier Dioctyl adipatePlasticizer 4.87 Plastomoll BASF DOA Diisononyl pthalate Plasticizer4.87 Plastomoll BASF DINP Isodecyl Plasticizer 4.87 Santicizer 148 Ferrodiphenylphosphate Rutile Titanium Intumescent 14.62 Kronos 2300 KronosDioxide Filler Pentaerythritol Intumescent 13.00 Charmor Perstorp FillerPM40 Melamine Intumescent 13.00 Melamine BASF Filler AmmoniumIntumescent 39.53 Exolit AP422 Clariant polyphosphate Filler Fatty AcidDispersing 0.73 Disperse 652, Tego derivative additive Evonik AlkylQuaternary Thixotropic 1.62 Garamite Rockwood Ammonium clay agent 1958Additives Ltd China Clay Thickening 2.06 Polywhite E Imerys AgentMinerals Ltd Benzenepropanoic Anti-oxidant 0.81 Irganox 1135 Ciba acid,3,5-bis (1,1- dimethyl-ethyl)-4- hydroxy-, C7-C9 branched alkyl estersMixing ratio 1^(st) part:2^(nd) part by weight=10.8:100

Properties:

Hardness development Tack free time: 45-60 minutes

-   -   2 hrs 45-50 Shore A    -   3 hrs 60-65 Shore A    -   6 hrs 70-75 Shore A    -   24 hrs 75-80 Shore A

Fire Testing:

Universal Column, 203×203×52, Hp/A 188 m⁻¹, DFT 3.95 mm.Nullifire 1.5 m³ Furnace, to BS476 pt20Time to Critical Temperature (550° C.)=91 minutes

1. An intumescent composition, comprising: a polymer selected from asilane-terminated polyurethane or a silane-terminated polyether; aplasticizer that is compatible with the polymer; and an intumescentingredient.
 2. The composition according to claim 1, wherein the polymeris a telechelic polymer with di- or tri-functional end-groups.
 3. Thecomposition according to claim 1, wherein the polymer has an alkoxygroup content of 0.35-0.70 mmol/g.
 4. The composition according to claim1, wherein the polymer has a methoxy group content of 0.35-0.70 mmol/g.5. The composition according to claim 1, wherein the plasticizercomprises a phthalate, an adipate, a sebacate, or a benzoate.
 6. Thecomposition according to claim 1, wherein the intumescent ingredientcomprises an intumescent filler composition comprising an acid source, acarbon source, and a gas source.
 7. The composition according to claim6, wherein the intumescent filler composition comprises titaniumdioxide, pentaerythritol, ammonium polyphosphate, and melamine.
 8. Thecomposition according to claim 1, further comprising a cross-linker. 9.The composition according to claim 1, wherein the composition is capableof swelling to at least three times its original volume when heated to500° C.
 10. The composition according to claim 1, wherein the amount ofintumescent ingredient present is selected from 40-80%, 50-75%, and55-75% by weight of the intumescent composition. 11-17. (canceled) 18.The composition according to claim 1, wherein the composition is capableof swelling to at least ten times its original volume when heated to500° C.
 19. The composition according to claim 1, wherein theintumescent ingredient is present in an amount of at least 20% by weightof the intumescent composition.
 20. The composition according to claim1, wherein the amount of polymer present is selected from 4-50%, 5-20%,and about 10% by weight of the intumescent composition.
 21. Thecomposition according to claim 1, wherein the plasticizer is present inan amount of at least 5% by weight of the intumescent composition. 22.The composition according to claim 1, further comprising a solvent. 23.A process for forming a cured intumescent substance, comprising:applying the composition according to claim 1 to a substrate; andallowing the composition to cure.
 24. A cured intumescent substanceobtainable by the process of claim
 23. 25. A building comprising a steelframework and coated thereon, the cured intumescent substance accordingto claim
 24. 26. A method of fire protecting a building framework,comprising: applying the composition according to claim 1 to thebuilding framework.
 27. The method according to claim 26, wherein thebuilding framework is a steel framework.